Electric storage battery construction and method of manufacture

ABSTRACT

An electric storage battery and method of manufacture thereof characterized by a feedthrough pin which is internally directly physically and electrically connected to an inner end of a positive electrode substrate. A C-shaped mandrel extends around the pin and substrate end enabling the pin/mandrel to be used during the manufacturing process as an arbor to facilitate winding layers of a spiral jellyroll electrode assembly. The pin additionally extends from the battery case and in the final product constitutes one of the battery terminals with the battery case comprising the other terminal. Active material is removed from both sides of the outer end of the negative electrode in the jellyroll to allow room for adhesive tape to secure the jellyroll. The electrolyte is injected through the open end of the case after the endcap is welded to the negative electrode but before sealing the endcap to the case. The electrolyte is preferably injected through the C-shaped mandrel to facilitate and speed filling.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/348,665, filed Jan. 15, 2002.

FIELD OF THE INVENTION

[0002] This invention relates generally to electric storage batteriesand more particularly to a battery construction, and method ofmanufacture thereof, suitable for use in implantable medical devices.

BACKGROUND OF THE INVENTION

[0003] Rechargeable electric storage batteries are commerciallyavailable in a wide range of sizes for use in a variety of applications.As battery technology continues to improve, batteries find newapplications which impose increasingly stringent specifications relatingto physical size and performance. Thus, new technologies have yieldedsmaller and lighter weight batteries having longer storage lives andhigher energy output capabilities enabling them to be used in anincreasing range of applications, including medical applications, where,for example, the battery can be used in a medical device which isimplanted in a patient's body. Such medical devices can be used tomonitor and/or treat various medical conditions.

[0004] Batteries for implantable medical devices are subject to verydemanding requirements, including long useful life, high power output,low self-discharge rates, compact size, high reliability over a longtime period, compatibility with the patient's internal body chemistry,etc. Although various battery chemistries have been tried, lithium iontechnology is generally accepted as the preferred chemistry for medicalimplant applications.

[0005] Such electric storage batteries are generally comprised of atubular metal case enveloping an interior cavity which contains anelectrode assembly surrounded by a suitable electrolyte. The electrodeassembly generally comprises a plurality of positive electrode, negativeelectrode, and separator layers which are typically stacked and/orspirally wound to form a jellyroll. The positive electrode is generallyformed of a metal substrate having positive active material coated onboth faces of the substrate. Similarly, the negative electrode is formedof a metal substrate having negative active material coated on bothfaces of the substrate. In forming an electrode assembly, separatorlayers are interleaved between the positive and negative electrodelayers to provide electrical isolation.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to an electric storage batteryincorporating one or more aspects described herein for enhancing batteryreliability while minimizing battery size. In addition, the invention isdirected to a method for efficiently manufacturing the battery at arelatively low cost.

[0007] In accordance with a first significant aspect of the invention, afeedthrough pin is provided which is directly physically andelectrically connected to the inner end of an electrode substrate (e.g.,positive), as by welding. The pin is used during the manufacturingprocess as an arbor to facilitate winding the layers to form anelectrode assembly jellyroll. Additionally, in the fully manufacturedbattery, the pin extends through a battery case endcap and functions asone of the battery terminals. The battery case itself generallyfunctions as the other battery terminal.

[0008] More particularly, in accordance with an exemplary preferredembodiment, the inner end of the positive electrode substrate is spotwelded to the feedthrough pin to form an electrical connection. Thesubstrate, e.g., aluminum, can be very thin, e.g., 0.02 mm, making itdifficult to form a strong mechanical connection to the pin, which ispreferably constructed of a low electrical resistance, highly corrosionresistant material, e.g., platinum iridium, and can have a diameter onthe order of 0.40 mm. In order to mechanically reinforce the pin andsecure the pin/substrate connection, a slotted C-shaped mandrel isprovided. The mandrel is formed of electrically conductive material,e.g., titanium-6AI-4V, and is fitted around the pin, overlaying thepin/substrate connection. The mandrel is then preferably welded to boththe pin and substrate. The mandrel slot defines a keyway foraccommodating a drive key which can be driven to rotate the mandrel andpin to wind the electrode assembly layers to form the spiral jellyroll.

[0009] In accordance with a further significant aspect of the invention,the outer layer of the jellyroll is particularly configured to minimizethe size, i.e., outer radius dimension, of the jellyroll. Moreparticularly, in the exemplary preferred embodiment, the active materialis removed from both faces of the negative electrode substrate adjacentits outer end. The thickness of each active material coat can be about0.04 mm and the thickness of the negative substrate can be about 0.005mm. By baring the outer end of the negative electrode substrate, it canbe adhered directly, e.g., by an appropriate adhesive tape, to the nextinner layer to close the jellyroll to while minimizing the roll outerradius dimension.

[0010] A battery case in accordance with the invention is comprised of atubular case body having open first and second ends. The feedthrough pinpreferably carries a first endcap physically secured to, butelectrically insulated from, the pin. This first endcap is preferablysecured to the case body, as by laser welding, to close the open firstend and form a leak free seal. With the jellyroll mounted in the caseand the first endcap sealed, the interior cavity can thereafter befilled with electrolyte from the open second end.

[0011] In accordance with a still further aspect of the invention, thejellyroll assembly is formed with a flexible electrically conductive tabextending from the negative electrode substrate for electricalconnection to the battery case. In accordance with a preferredembodiment, the tab is welded to a second endcap which is in turn weldedto the case. The tab is sufficiently flexible to enable the secondendcap to close the case body second end after the interior cavity isfilled with electrolyte via the open second end. In accordance with anexemplary preferred embodiment, the tab is welded to the inner face ofthe second endcap such that when the jellyroll is placed in the body,the tab locates the second endcap proximate to the body withoutobstructing the open second end. After electrolyte filling, the casebody is sealed by bending the tab to position the second endcap acrossthe body second end and then laser welding the endcap to the case body.

BRIEF DESCRIPTION OF THE FIGURES

[0012]FIG. 1 is a side view of a feedthrough pin subassembly inaccordance with the invention;

[0013]FIG. 2 is a longitudinal sectional view through the subassembly ofFIG. 1;

[0014]FIG. 3 is a plan view of a positive electrode strip utilized inthe exemplary preferred electrode assembly in accordance with theinvention;

[0015]FIG. 4 is a side view of the positive electrode strip of FIG. 3;

[0016]FIG. 5 is an enlarged sectional view of the area A of FIG. 4showing the inner end of the positive electrode strip of FIGS. 3 and 4;

[0017]FIG. 6 is an isometric view showing the bared inner end of thepositive electrode substrate spot welded to the feedthrough pin andconfigured to receive a C-shaped mandrel thereon;

[0018]FIG. 7 is an end view showing the C-shaped mandrel being crimpedto the pin and electrode;

[0019]FIG. 8 is an end view showing the C-shaped mandrel mounted on thepin and capturing the positive electrode substrate therebetween;

[0020]FIG. 9 is an isometric view depicting a drive key accommodated inthe slot of the C-shaped mandrel;

[0021]FIG. 10 is a plan view showing the drive key coupled to a drivemotor for rotating the C-shaped mandrel;

[0022]FIG. 11 is a schematic end view depicting how rotation of theC-shaped mandrel and pin can wind positive electrode, negativeelectrode, and separator strips to form a spiral jellyroll electrodeassembly;

[0023]FIG. 12 is a plan view of a negative electrode strip utilized inthe exemplary preferred electrode assembly in accordance with theinvention;

[0024]FIG. 13 is a side view of the negative electrode strip of FIG. 12;

[0025]FIG. 14 is an enlarged sectional view of the area A of FIG. 13showing the inner end of the negative electrode strip of FIGS. 12 and13;

[0026]FIG. 15 is an enlarged sectional view of the area B of FIG. 13showing the outer end of the negative electrode strip of FIGS. 11 and12;

[0027]FIG. 16 is an isometric view showing that the layers of a spirallywound electrode assembly, i.e., jellyroll;

[0028]FIG. 17 is a plan view of the negative electrode strip showing theattachment of a flexible electrically conductive tab to the bared outerend of the negative electrode substrate;

[0029]FIG. 18 is an enlarged sectional view showing how the outer turnof the negative electrode strip is taped to the next inner layer toclose the jellyroll to minimize its outer radius dimension;

[0030]FIG. 19 is an isometric view depicting the jellyroll electrodeassembly being inserted into a cylindrical battery case body;

[0031]FIG. 20 is an isometric view showing a battery case body with thenegative electrode tab extending from the open case body;

[0032]FIG. 21 is an isometric view showing how the negative electrodetab is mechanically and electrically connected to an endcap for sealingthe case body second end;

[0033]FIG. 22 is a side view showing how the negative electrode tabholds the second endcap proximate to the case body second end withoutobstructing the open second end;

[0034]FIG. 23 is a front view showing the weld position and therelationship between the various components; and

[0035]FIG. 24 is an enlarged sectional view of the second end of thebattery case showing the endcap in sealed position.

DETAILED DESCRIPTION

[0036] Attention is initially directed to FIGS. 1 and 2 which illustratea preferred feedthrough pin subassembly 10 utilized in accordance withthe present invention. The subassembly 10 is comprised of an elongatepin 12, preferably formed of a solid electrically conductive material,having low electrical resistance and high corrosion resistance such asplatinum iridium, preferably 90Pt/10Ir. The pin 12 extends through, andis hermetically sealed to a header 14. The header 14 is comprised ofdielectric disks, e.g., ceramic, 16 and 18 which sandwich a glass hollowcylinder 20 therebetween. The glass hollow cylinder is hermeticallysealed to the pin 12. The outer surface of the glass hollow cylinder 20is sealed to the inner surface of an electrically conductive hollowmember 22, e.g., titanium-6Al-4V. As will be seen hereinafter, theconductive hollow material 22 functions as a battery case endcap in thefinal product to be described hereinafter.

[0037] Attention is now directed to FIGS. 3, 4, and 5 which illustrate apreferred positive electrode strip 30 which is utilized in thefabrication of a preferred spirally wound jellyroll electrode assemblyin accordance with the present invention. The positive electrode strip30 is comprised of a metal substrate 32 formed, for example, ofaluminum. Positive electrode active material 34, 36 is deposited,respectively on the upper and lower faces 38 and 40 of the substrate 32.Note in FIGS. 3, 4, and 5 that the right end of the substrate 32 isbare, i.e. devoid of positive active material on both the upper andlower faces 38, 40.

[0038] It is to be pointed out that exemplary dimensions are depicted inFIGS. 1-5 and other figures herein. These exemplary dimensions areprovided primarily to convey an order of magnitude to the reader tofacilitate an understanding of the text and drawings. Although theindicated dimensions accurately reflect one exemplary embodiment of theinvention, it should be appreciated that the invention can be practicedutilizing components having significantly different dimensions.

[0039]FIG. 6 depicts an early process step for manufacturing a batteryin accordance with the invention utilizing the pin subassembly 10 (FIGS.1, 2) and the positive electrode strip 30 (FIGS. 3-5). A topsideelectrode insulator (not shown), which may comprise a thin disk ofDuPont Kapton® polyimide film, is slipped onto the pin 12 adjacent theheader 14. In accordance with the present invention, the bare end of theelectrode strip substrate 32 is electrically connected to the pin 12preferably by resistance spot welding, shown at 44. Alternatively,substrate 32 may be ultrasonically welded to the pin 12. The thinness,e.g. point 0.02 mm of the substrate 32, makes it very difficult to forma strong mechanical connection between the substrate and the pin 12.Accordingly, in accordance with a significant aspect of the presentinvention, an elongate C-shaped mandrel 48 is provided to mechanicallyreinforce the pin 12 and secure the substrate 32 thereto.

[0040] The mandrel 48 preferably comprises an elongate titanium ortitanium alloy such as Ti-6Al-4V tube 50 having a longitudinal slot 52extending along the length thereof. The arrow 54 in FIG. 6 depicts howthe mandrel 48 is slid over the pin 12 and substrate 32, preferablyoverlaying the line of spot welds 44. The mandrel 48, pin 12, andsubstrate 32 are then preferably welded together, such as by resistancespot welding or by ultrasonic welding. Alternatively, the mandrel 48 maybe crimped onto the pin 12 at least partially closing the “C” to createa strong mechanical connection. In the case of forming only a mechanicalconnection and not necessarily a gas-tight electrical connection betweenthe mandrel 48 and the pin and substrate, the mandrel material ispreferably made of a material that will not lead to electrolysis. Whenused with electrolytes that tend to contain hydrofluoric acid, themandrel is preferably made of 304, 314, or 316 stainless steels oraluminum or an alloy thereof chosen for its compatibility with the othermaterials. FIG. 7 is an end view showing the step of crimping themandrel 48 to the pin 12 and substrate 32. Supporting die 126 is used tosupport the mandrel 48 and crimping dies 124 and 125 are used to deformthe edges of the mandrel 48 to bring them closer together andmechanically connect the mandrel 48 to the pin 12 and substrate 32. Bycrimping in the direction of arrows 127 and 128, a strong connection isformed without damaging the thin electrode or disturbing the electricalconnection between the pin and the electrode.

[0041]FIG. 8 is an end view showing the slotted mandrel 48 on the pin 12with the substrate 32 extending tangentially to the pin 12 andterminating adjacent the interior surface of the mandrel tube 50. Thetube 50 is preferably sufficiently long so as to extend beyond the freeend of the pin 12. As depicted in FIG. 9, this enables a drive key 56 toextend into the mandrel slot 52.

[0042]FIG. 10 schematically depicts a drive motor 60 for driving thedrive key 56 extending into mandrel slot 52. With the pin subassemblyheader 14 supported for rotation (not shown), energization of the motor60 will orbit the key drive 56 to rotate the mandrel 48 and subassembly10 around their common longitudinal axes. The rotation of the mandrel 48and subassembly 10 is employed to form a jellyroll electrode assembly inaccordance with the present invention.

[0043] More particularly, FIG. 11 depicts how a jellyroll electrodeassembly is formed in accordance with the present invention. The bareend of the substrate 32 of the positive electrode strip 30 iselectrically connected to the pin 12 as previously described. Theconductive mandrel 48 contains the pin 12 and bare substrate end, beingwelded to both as previously described. A strip of insulating separatormaterial 64 extending from opposite directions is introduced between themandrel 48 and positive electrode substrate 32, as shown. A negativeelectrode strip 70 is then introduced between the portions of theseparator material extending outwardly from mandrel 48.

[0044] The preferred exemplary negative electrode strip 70 is depictedin FIGS. 12-15. The negative electrode strip 70 is comprised of asubstrate 72, e.g. titanium, having negative active material formed onrespective faces of the substrate. More particularly, note in FIG. 14that negative active material 74 is deposited on the substrate uppersurface 76 and negative active material 78 is deposited on the substratelower surface 80. FIG. 14 depicts the preferred configuration of theinner end 82 of the negative electrode strip 70 shown at the left ofFIGS. 12 and 13. FIG. 15 depicts the configuration of the outer end 83of the negative electrode strip 70 shown at the right side of FIGS. 12and 13.

[0045] Note in FIG. 14 that one face of the substrate inner end 82 isbared. This configuration can also be noted in FIG. 11 which shows howthe negative substrate inner end 82 is inserted between turns of theseparator strip 64. After the strip 70 has been inserted as depicted inFIG. 11, the aforementioned drive motor 60 is energized to rotate pin 12and mandrel 48, via drive key 56, in a counterclockwise direction, asviewed in FIG. 11. Rotation of pin 12 and mandrel 48 functions to windpositive electrode strip 30, separator strip 64, and negative electrodestrip 70, into the spiral jellyroll assembly 84, depicted in FIG. 16.The assembly 84 is comprised of multiple layers of strip material sothat a cross section through the assembly 84 would reveal a sequence oflayers in the form pos/sep/neg/sep/pos/sep/neg/ . . . , etc.

[0046]FIG. 15 depicts a preferred configuration of the outer end 83 ofthe negative electrode strip 70. Note that the outer end 88 of thesubstrate 72 is bared on both its top and bottom faces. Additionally, asshown in FIG. 17, a flexible metal tab 90 is welded crosswise to thesubstrate 72 so as to extend beyond edge 92. More particularly, notethat portion 94 of tab 90 is cantilevered beyond edge 92 of negativeelectrode strip 70. This tab portion, as will be described hereinafter,is utilized to mechanically and electrically connect to an endcap forclosing a battery case.

[0047] Attention is now called to FIG. 18, which illustrates a preferredtechnique for closing the jellyroll assembly 84. That is, the bared end88 of the negative electrode substrate 72 extending beyond the negativeactive material coat 78 is draped over the next inner layer of thejellyroll assembly 84. The end 88 can then be secured to the next innerlayer, e.g., by appropriate adhesive tape 96. One such suitable adhesivetape is DuPont Kapton® polyimide tape. It is important to note that theouter end configuration 88 of the negative electrode strip 70 enablesthe outer radius dimension of the jellyroll assembly 84 to be minimizedas shown in FIG. 18. More particularly, by baring the substrate 72beyond the active material 78, the tape 96 is able to secure thesubstrate end without adding any radial dimension to the jellyrollassembly. In other words, if the outer end of the substrate were notsufficiently bared, then the tape 96 would need to extend over theactive material and thus add to the outer radius dimension of thejellyroll 84. Furthermore, the bare substrate 72 is more flexible thanthe substrate coated with active material 78 and conforms more readilyto the jellyroll assembly 84, making it easier to adhere it to thesurface of the jellyroll. These space savings, although seemingly small,can be clinically important in certain medical applications. It shouldbe noted that the electrode need only be bared at an end portion longenough to accommodate the tape 96, as shown in FIG. 18. Because theuncoated substrate does not function as an electrode, it would wastespace in the battery to bare any more than necessary to accommodate thetape. In a preferred embodiment, the length of uncoated substrate isbetween 1 and 8 mm, and more preferably about 2 mm.

[0048]FIG. 19 depicts the completed jellyroll assembly 84 and shows thecantilevered tab portion 94 prior to insertion into a battery case body100. The case body 100 is depicted as comprising a cylindrical metaltube 101 having an open first end 104 and open second end 106. Arrow 107represents how the jellyroll assembly 84 is inserted into thecylindrical tube 101. FIG. 20 depicts the jellyroll assembly 84 withinthe tube 101 with the cantilevered negative electrode tab 94 extendingfrom the case open second end 106. The case open first end 104 is closedby the aforementioned header 14 of the pin subassembly 10 shown in FIGS.1 and 2. More particularly, note that the metal hollow member 22 isconfigured to define a reduced diameter portion 108 and shoulder 110.The reduced diameter portion 108 is dimensioned to fit into the open end104 of the cylindrical tube 101 essentially contiguous with the tube'sinner wall surface. The shoulder 110 of the hollow member 22 engages theend of the case tube 101. This enables the surfaces of the reduceddiameter portion 108 and shoulder 110 to be laser welded to the end ofthe case 100 to achieve a hermetic seal.

[0049] Attention is now directed to FIGS. 21-24, which depict the tab 94extending from the second open end 106 of the case tube 101. Note thatthe tab 94 extends longitudinally from the body close to the case tubeadjacent to tube's inner wall surface. In accordance with a preferredembodiment of the invention, the tab 94 is welded at 110 to the innerface 112 of a circular second endcap 114. In accordance with a preferredembodiment, the tab 94 is sufficiently long to locate the weld 110beyond the center point of the circular endcap 114. More particularly,note in FIGS. 21-24 that by locating the weld 110 displaced from thecenter of the cap 114, the tab 94 can conveniently support the endcap114 in a vertical orientation as depicted in FIG. 22 misaligned withrespect to the open end 106. This end cap position approximatelyperpendicular to the end 122 of the case 100 is a first bias positionwherein the end cap advantageously tends to remain in that orientationwith the case end open prior to filling. To further describe therelationship between the weld location and the various components, FIG.23 shows a front view with various dimensions. L represents the lengthfrom the weld 110 to the top of the case 100 as measured parallel to theedge of the case. R is the radius of the end cap 114. For the preferredgeometry, L≦2R. Weld 110 is preferably made above the center point 111of the end cap 114. Preferably, the end cap 114 overlaps the case 100 byapproximately R/2. By configuring the tab 94 and weld 110 as indicated,the endcap 114 can be supported so that it does not obstruct the openend 106, thereby facilitating electrolyte filling of the case interiorcavity via open end 106. A filling needle or nozzle can be placedthrough open end 106 to fill the case. This obviates the need for aseparate electrolyte fill port, thereby reducing the number ofcomponents and number of seals to be made, thus reducing cost andimproving reliability. Furthermore, for small medical batteries, the endcaps would be very small to have fill ports therein. In a preferredembodiment in which the case wall is very thin, for example, 0.002inches, providing a fill port in the side wall of the case would beimpractical. Even in the case of larger devices where space is lesscritical and the wall is more substantial, providing a fill port in theside of the case would mean the electrolyte would have a very long pathlength to wet the jellyroll. Note that while the case could be filledwith electrolyte prior to welding tab 94 to endcap 114, it would bedifficult and messy to do so. Therefore, it is advantageous to configurethe tab 94 and weld 110 as described to allow the weld to be made priorto filling.

[0050] Preferably before filling, a bottomside electrode insulator (notshown), which may comprise a thin disk of DuPont Kapton® polyimide film,is installed into the case between the rolled electrode assembly and thestill open end of the battery case.

[0051] In a preferred filing method, there is a channel of air betweenthe pin and the crimped or welded C-shaped mandrel, which is used as aconduit for quickly delivering the electrolyte to the far end of thebattery and to the inside edges of the electrodes within the jellyroll.Filling from the far end of the battery prevents pockets of air frombeing trapped, which could form a barrier to further filling. Thisfacilitates and speeds the filling process, ensuring that electrolytewets the entire battery.

[0052] Thereafter, the flexible tab 94 can be bent to the configurationdepicted in FIG. 24. Note that the endcap 114 is configured similarly toheader hollow member 22 and includes a reduced diameter portion 118 anda shoulder 120. The reduced diameter portion snugly fits against theinner surface of the wall of tube 101 with the endcap shoulder 120bearing against the end 122 of the cylindrical case 100. The relativelylong length of the tab 94 extending beyond the center point of theendcap surface 112 minimizes any axial force which might be exerted bythe tab portion 94 tending to longitudinally displace the endcap 114.The end cap position covering the end 122 of the case 100 is a secondbias position wherein the end cap advantageously tends to remain in thatorientation prior to welding. With the endcap in place, it can then bereadily welded to the case wall 101 to hermetically seal the battery.With tab 90 welded to negative substrate 72 and with the negativeelectrode strip 70 as the outermost layer of the jellyroll, the endcap114 becomes negative. In turn, welding the endcap 114 to the case 100renders the case negative.

[0053] From the foregoing, it should now be appreciated that an electricstorage battery construction and method of manufacture have beendescribed herein particularly suited for manufacturing very small,highly reliable batteries suitable for use in implantable medicaldevices. Although a particular preferred embodiment has been describedherein and exemplary dimensions have been mentioned, it should beunderstood that many variations and modifications may occur to thoseskilled in the art falling within the spirit of the invention and theintended scope of the appended claims.

We claim:
 1. An electric storage battery including: a case comprising aperipheral wall defining an interior volume; and an electrode assemblymounted in said interior volume, said electrode assembly including: anelectrically conductive elongate pin; and first and second oppositepolarity electrode strips wound together to form a spiral roll, eachelectrode strip having inner and outer ends, wherein said firstelectrode strip is electrically coupled to said pin at said inner end;and a hollow elongate mandrel closely fitted around said pin formechanically reinforcing said pin.
 2. The battery of claim 1 whereinsaid pin extends exteriorly of said case peripheral wall to function asa first battery terminal.
 3. The battery of claim 1 wherein said mandrelis electrically coupled to said pin.
 4. The battery of claim 1 whereinsaid first electrode strip inner end is directly connected to said pinby at least one weld.
 5. The battery of claim 1 wherein said pinconsists of a Ptlr alloy.
 6. The battery of claim 1 further comprising afirst end cap mounted on said pin, said first end cap including anelectrical insulator; and wherein said pin extends through and ishermetically sealed to said end cap electrical insulator.
 7. The batteryof claim 1 wherein said mandrel defines an elongate slot; and whereinsaid first electrode strip extends through said mandrel slot.
 8. Thebattery of claim A1 wherein said mandrel is welded to said pin.
 9. Thebattery of claim A1 wherein said mandrel comprises titanium or an alloythereof.
 10. An electric storage battery made by the steps of: providingan electrically conductive elongate pin having inner and outer ends;providing a first polarity electrode strip; providing a second polarityelectrode strip; electrically connecting a first end of the firstpolarity electrode strip to the pin proximate to the pin inner end;mounting a reinforcing mandrel on the pin; and winding together thefirst polarity electrode strip and the second polarity electrode stripto form a spiral roll having at least a portion of the pin within thespiral roll.
 11. The battery of claim 10 wherein said steps furtherinclude the step of mounting the spiral roll in a case with the pinouter end extending exteriorly of the case to form a first batteryterminal.
 13. The battery of claim 10 wherein said steps further includthe step of electrically coupling the reinforcing mandrel to the pin.14. The battery of claim 10 wherein said step of winding together thefirst polarity electrode strip and the second polarity electrode stripcomprises rotating the pin.
 15. The battery of claim 10 wherein saidstep of providing an electrically conductive elongate pin includes astep of: forming an end cap including an insulating member on the pinhermetically sealed thereto and positioned proximate to but spaced fromthe pin outer end.
 16. The battery of claim 3 wherein said steps furtherinclude a step of mounting a conductive member around the insulatingmember; and electrically connecting the conductive member to the case.17. The battery of claim 1 wherein said steps further include a step ofwelding the reinforcing mandrel to the pin.
 18. The battery of claim 1wherein the mandrel comprises a tube having a slot therein and whereinsaid winding step further includes the steps of: inserting a drive keyinto the slot; and orbiting the drive key to rotate the mandrel and pin.19. The battery of claim 1 wherein the mounted mandrel comprises achannel and wherein said steps further include a step of injectingelectrolyte through the channel.
 20. A method of constructing anelectric storage battery including: providing an electrically conductiveelongate pin having inner and outer ends; providing a first polarityelectrode strip; providing a second polarity electrode strip;electrically connecting a first end of said first polarity electrodestrip to said pin proximate to said pin inner end; mounting areinforcing mandrel on the pin; winding together said first polarityelectrode strip and said second polarity electrode strip to form aspiral roll having at least a portion of the pin within the spiral roll.21. The method of claim 20 and further including the step of: mountingsaid spiral roll in a case with said pin outer end extending exteriorlyof said case to form a first battery terminal.
 22. The method of claim20 and further including the step of: electrically coupling thereinforcing mandrel to the pin.
 23. The method of claim 20 wherein saidstep of winding together the first polarity electrode strip and thesecond polarity electrode strip comprises rotating the pin.
 24. Themethod of claim 20 wherein said step of providing said electricallyconductive elongate pin includes a step of: forming an end cap includingan insulating member on said pin hermetically sealed thereto andpositioned proximate to but spaced from said pin outer end.
 25. Themethod of claim 24 including the further step of mounting a conductivemember around said insulating member; and electrically connecting saidconductive member to said case.
 26. The method of claim 20 including afurther step of welding the reinforcing mandrel to the pin.
 27. Themethod of claim 20 said step of mounting a reinforcing mandrel comprisesmounting a mandrel comprising a tube having a slot therein; and whereinsaid winding step further includes the steps of: inserting a drive keyinto the slot; and orbiting the drive key to rotate the mandrel and pin.28. The method of claim 20 wherein the said step of mounting areinforcing mandrel comprises providing a channel and wherein said stepsfurther include a step of injecting electrolyte through the channel. 29.An electrode assembly including: an electrically conductive, elongatepin; an elongate reinforcing mandrel mounted on at least a portion ofsaid pin; and a spiral roll comprising first and second oppositepolarity electrode strips and at least one separator strip separatingsaid electrode strips mounted on said pin, wherein one of said electrodestrips is electrically coupled to said pin.
 30. The electrode assemblyof claim 29 wherein said mandrel is C-shaped and defines a longitudinalslot; and wherein an inner end of said first electrode strip extendsthrough said mandrel slotand is electrically connected to said pin. 31.The electrode assembly of claim 29 wherein said pin comprises a portionextending beyond said spiral roll to form a battery terminal.
 32. Theelectrode assembly of claim 29 wherein said mandrel is crimped onto saidpin.
 33. The electrode assembly of claim 29 wherein the mounted mandrelhas a channel through which electrolyte can be injected.
 34. Anelectrode assembly made by the steps of: providing an electricallyconductive, elongate pin; providing a first polarity electrode strip;providing a second polarity electrode strip; electrically connecting afirst end of the first polarity electrode strip to the pin; mounting areinforcing mandrel on the pin; and winding together the first polarityelectrode strip and the second polarity electrode strip to form a spiralroll having at least a portion of the pin and the mandrel interior tothe spiral roll.
 35. The assembly of claim 34 wherein said steps furtherinclude a step of crimping the reinforcing mandrel to the pin.
 36. Theassembly of claim 34 wherein said steps further include a step ofwelding the reinforcing mandrel to the pin.
 37. The assembly of claim 34wherein said step of winding together the first polarity electrode stripand the second polarity electrode strip comprises rotating the pin andthe mandrel.
 38. The assembly of claim 34 wherein said step of windingtogether the first polarity electrode strip and the second polarityelectrode strip to form a spiral roll comprises leaving a portion of thepin extending beyond the spiral roll to form a battery terminal.
 39. Amethod of constructing an electric storage battery including: providingan electrically conductive, elongate pin; providing a first polarityelectrode strip; providing a second polarity electrode strip;electrically connecting a first end of said first polarity electrodestrip to said pin; mounting a reinforcing mandrel on said pin; andwinding together the first polarity electrode strip and the secondpolarity electrode strip to form a spiral roll.
 40. The method of claim39 including the further step of crimping the reinforcing mandrel to thepin.
 41. The method of claim 39 including the further step of weldingthe reinforcing mandrel to the pin.
 42. The method of claim 39 whereinsaid step of winding together the first polarity electrode strip and thesecond polarity electrode strip comprises rotating the pin and themandrel.
 42. The method of claim 39 wherein said step of windingtogether the first polarity electrode strip and the second polarityelectrode strip to form a spiral roll comprises leaving a portion of thepin extending beyond the spiral roll to form a battery terminal.
 43. Anelectric storage battery comprising: an electrically conductive casesealed by first and second end caps; an electrically conductive terminalpin extending through said first end cap and electrically insulated fromsaid case; an electrode assembly disposed within said case andcomprising first and second opposite polarity electrodes separated byseparators wherein said first electrode is electrically coupled to saidpin; a flexible conductive tab electrically coupled to said secondelectrode proximate a first location at the seal formed between saidsecond end cap and said case; wherein said second end cap has a centerand wherein said second end cap has a width from said first location toa second location at the seal formed between said second end cap andsaid case measured along a line through said center; and said tabelectrically connected to said second end cap at a third locationbetween said second location and said center of said second end cap. 44.The battery of claim 43 wherein said case has no separate fill hole. 45.The battery of claim 43 wherein said second end cap is welded to saidtab flat against an inner face of said second end cap.
 46. The batteryof claim 43 wherein said second end cap is circular and wherein saidwidth is a diameter.
 47. An electric storage battery made by the stepsof: providing a case comprising a peripheral wall of electricallyconductive material defining an interior volume and having first andsecond wall openings communicating with the interior volume; providingan electrically conductive terminal pin extending through a first endcap and electrically insulated from the case providing an electrodeassembly comprising first and second opposite polarity electrodeselectrically connecting the first electrode to the pin; forming aflexible conductive tab extending beyond a second edge of the electrodeassembly and electrically connected to the second electrode; mountingthe electrode assembly in the interior volume with the pin extending outthrough the first wall opening and the tab extending out through thesecond wall opening; mounting the first end cap to seal the first wallopening; providing a second end cap of electrically conductive material;and fastening the second end cap to the tab in a manner to provide anelectrical connection therebetween.
 48. The electric storage battery ofclaim 47 wherein said steps further include a further step of depositingelectrolyte into the case through the second wall opening following saidstep of fastening the second end cap to the tab.
 49. The electricstorage battery of claim 47 wherein said step of fastening the secondend cap to the tab includes welding the tab flat against an inner faceof the second end cap.
 50. The electric storage battery of claim 49including the further step of mounting the end cap in the second wallopening to seal the second wall opening.
 51. A method of constructing anelectric storage battery including: providing a case comprising aperipheral wall of electrically conductive material defining an interiorvolume and having first and second wall openings communicating with theinterior volume; providing an electrically conductive terminal pinextending through a first end cap and electrically insulated from thecase providing an electrode assembly comprising first and secondopposite polarity electrodes wherein the first electrode is electricallyconnected to the pin; forming a flexible conductive tab extending beyonda second edge of the electrode assembly and electrically connected tothe second electrode; mounting the electrode assembly in the interiorvolume with the pin extending out through the first wall opening and thetab extending out through the second wall opening; mounting the firstend cap to seal the first wall opening; providing a second end cap ofelectrically conductive material; and fastening the second end cap tothe tab in a manner to provide a mechanical and electrical connectiontherebetween.
 52. The method of claim 51 including a further step ofdepositing electrolyte into the case through the second wall openingafter said step of fastening the second end cap to the tab.
 53. Themethod of claim 51 wherein said step of fastening the second end cap tothe tab includes welding the tab flat against an inner face of thesecond end cap.
 54. The method of claim 53 including the further step ofmounting the end cap in the second wall opening to seal the second wallopening.
 55. An electric storage battery comprising: an electricallyconductive case hermetically sealed by first and second end caps,wherein said case has no separate fill holes and wherein said first andsecond end caps have no separate fill holes; an electrically conductiveterminal pin extending through said first end cap and electricallyinsulated from said case; an electrode assembly disposed within saidcase and comprising first and second opposite polarity electrodesseparated by separators wherein said first electrode is electricallycoupled to said pin; and a flexible conductive tab electrically coupledto said second electrode and to said second end cap.
 56. An electricstorage battery made by the steps of: providing a case comprising aperipheral wall of electrically conductive material defining an interiorvolume and having first and second wall openings communicating with theinterior volume; providing an electrically conductive terminal pinextending through the first end cap and electrically insulated from thecase; providing an electrode assembly comprising first and secondopposite polarity electrodes electrically coupling the first electrodeto the pin; mounting the electrode assembly in the interior volume withthe pin extending out through the first wall opening; mounting the firstend cap to seal the first wall opening; providing a second end cap ofelectrically conductive material; and electrically coupling the secondelectrode to the second end cap; depositing electrolyte into the casethrough the second wall opening; and mounting the end cap in the secondwall opening to seal the second wall opening.
 57. The electric storagebattery of claim 56 wherein the step of electrically coupling the secondelectrode to the second end cap precedes the step of depositingelectrolyte into the case through the second wall opening.
 58. A methodof constructing an electric storage battery including: providing a casecomprising a peripheral wall of electrically conductive materialdefining an interior volume and having first and second wall openingscommunicating with the interior volume; providing an electricallyconductive terminal pin extending through the first end cap andelectrically insulated from the case; providing an electrode assemblycomprising first and second opposite polarity electrodes electricallycoupling the first electrode to the pin; mounting the electrode assemblyin the interior volume with the pin extending out through the first wallopening; mounting the first end cap to seal the first wall opening;providing a second end cap of electrically conductive material; andelectrically coupling the second electrode to the second end cap;depositing electrolyte into the case through the second wall opening;and mounting the end cap in the second wall opening to seal the secondwall opening.
 59. The method of claim 58 wherein the step ofelectrically coupling the second electrode to the second end capprecedes the step of depositing electrolyte into the case throughthe-second wall opening.
 60. A hermetically sealable electric storagebattery comprising: a case having an open end; a first electricallyconductive terminal electrically insulated from said case; an electrodeassembly disposed within said case and comprising first and secondopposite polarity electrodes separated by separators wherein said firstelectrode is electrically coupled to said first terminal; a flexibleconductive tab electrically coupled to said second electrode proximate afirst location at said case open end; said tab electrically connected tosaid end cap at a second location whereby said end cap has a first biasposition tending to keep said case open end open and a second biasposition tending to close said case open end.
 61. The battery of claim60 wherein said first bias position orients said end cap approximatelyperpendicular to said open end.
 62. The battery of claim 60 wherein saidsecond end cap is welded to said tab flat against an inner face of saidsecond end cap.
 63. The battery of claim 60 wherein: said end cap iscircular and has a radius R; the distance from said second location tosaid case open end is a length L; and L≦2R.
 64. The battery of claim 63wherein said second location is above the center of said end cap in saidfirst bias position.
 65. The battery of claim 63 wherein said end capoverlaps the case by approximately R/2 in said second bias position.